1. Field of the Invention
The present invention relates to a body activity controlled heart pacer provided for being positioned at or in the body of a patient.
2. Description of the Prior Art
European patent application No. 0 089 014 (Plicchi et al.) describes a body activity controlled heart pacer, which utilizes a respiration signal, that is derived from a body impedance measurement, as a body activity signal. The electrodes for measuring the body impedance are positioned in a body location which is different from the heart pacer capsule location. Furthermore, the electrodes are connected by leads (wire) to stimulation pulse rate controlling means inside the pacer capsule. A lead connection is, however, technically too complicated, especially if a plurality of sensors is employed.
A similar rate adaptive pacer is depicted in U.S. Pat. No. 4,428,378 (Anderson et al.). This pacer utilizes a motion sensor instead of an impedance (respiration) sensor to measure body activity. The motion sensor is inserted in the pacer capsule and again connected by wire to the remaining pacer components inside the pacer capsule. External body activity connection leads are not required in this case; the pacer capsule nevertheless becomes more voluminous.
Finally, another body activity controlled pacer is being marketed by Siemens-Elema under the name SENSOLOG 703 (See, for example, Siemens brochure A91003-M3372-L943-01-7600). A piezoelectric sensor is also used in this case. The signals are, however, processed differently from Anderson et al.